The present invention is directed to a lighting tube of the flexible, transparent type for housing miniature lamps. Such tubes are well-known. See U.S. Pat. Nos. 3,755,663, 4,263,640 and 4,271,458.
It is desireable to protect the miniature lamps and lamp conductors (wires) housed within the tube from moisture which may degrade the performance and structural integrity of the lamps and lamp conductors. In U.S. Pat. No. 4,271,458, a moisture resistant lighting tube is disclosed wherein viscous dielectric liquid such as mineral oil is introduced within the tube interior. The liquid surrounds the miniature lamps and conductors. Sealant slugs (silicone caulk or polysulphide) seal the end portions of the tube at which connectors are mounted. The assembly technique proposed in U.S. Pat. No. 4,271,458 is to insert the sealant slugs and connectors at the tube ends. Thereafter, a pair of small holes are drilled through the tube waller, a pair of small holes are drilled through the tube wall proximal the inside face of each sealant slug. One whole provides an entry port for the viscous liquid, and the other provides a suction port for the liquid. The liquid is drawn into the tube by suction. An air pocket is formed within the tube interior to accommodate internal pressure variations due to temperature changes. The holes are then sealed at the exterior with unplasticized viny film and adhesive.
In U.S. Pat. No. 4,271,458, the juction or connection point of the lamp conductors and each connector is encapsulated in the sealant slug. The sealant slugs are sufficiently resilient whereby the slugs do not provide ample strain relief for the electrical junction. The slugs are also capable of being dislodged whereby the integrity of the end seal can be broken and the lamps and conductors inadvertently extracted from the tube interior. Lighting tubes of this type may also use a gelatinous substance to fill the tube interior. Such a substance is thought to be less likely to flow through small cracks which may develop in the tube wall. The substance envelops the lamp circuit. If any of the lamps fail, the lamp circuit cannot be conveniently extracted and repaired because the substance tends to cling to the lamps and the circuit, making it difficult to remove the circuit without injuring the lamps or conductors.
The problem solved by the present invention is that of providing a moisture resistant tube for housing miniature lamps which provides superior strain relief at the electrical junction between the lamp conductors and the end connectors and which can be easily dismantled to repair the lamp circuit without injuring it.